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Sandwich panel with interior barrier

a sandwich panel and interior barrier technology, applied in the field of sandwich panel with interior barrier, can solve the problems of reducing the overall strength of the sandwich panel, reducing the amount of voids and other imperfections of certain types of skins and adhesives, and increasing the mold pressure generally has little effect, so as to reduce the effect of substantially reducing the amount of voids and other imperfections

Inactive Publication Date: 2005-02-03
HEXCEL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0010] In accordance with the present invention methods are provided for producing sandwich panels in which the amount of voids and imperfections in the skins and / or skin adhesive is substantially reduced. The invention is based in part on the discovery that the interior of the sandwich panel can be pressurized during molding to provide an outward pressure against the interior surface of the adhesive and / or skins. This pressure functions as a counter pressure or force against the pressure or force exerted by the mold against the exterior surface of the skins. It was found that the use of such counter pressure is useful in reducing the amount of voids and other imperfections in the adhesive and / or skins.
[0013] The present invention is useful for making a wide variety of sandwich panels that may be used in numerous different applications. The invention is particularly well suited for use in making sandwich panels where a honeycomb or foam core is bonded to thermosetting or thermoplastic prepreg composite skins and cured using heat and pressure in a mold to form the final sandwich panel. The use of an interior barrier and core counter pressure not only reduces the amount of voids and imperfections in the final composite skin, but also provides a permanent interior barrier that remains as an integral part of the panel. A permanent internal barrier is useful in situations where the final skins may be porous or susceptible to the development of cracks.

Problems solved by technology

Poor bonding of the skins to the core causes a substantial reduction in the overall strength of the sandwich panel.
There is a tendency for certain types of skins and adhesives to develop voids or other imperfections during final processing of the sandwich panels in the mold.
Increasing the mold pressure generally has little effect and may sometimes make the problem worse.

Method used

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Examples

Experimental program
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Effect test

example 1

All Thermosetting Materials where Extra Adhesives are Used—FIGS. 1 and 4

[0038] A sandwich panel in accordance with the present invention was prepared using aluminum honeycomb as the core material. The honeycomb was perforated for internal ventilation and had a cell size of {fraction (1 / 2)} inch. The core was 11.5 inches long, 11.5 inches wide and 1.00 inch thick. The honeycomb was placed between two sheets of CAPRAN 526 Nylon 6 / 6 film that was 0.003 inch thick. This particular Nylon film is available from Honeywell Corp. (Buffalo, N.Y.). Each of the Nylon films was 15 inches wide and 15 inches long so that they overlapped the edges of the honeycomb. The resulting flashing of Nylon film surrounding the honeycomb was compression sealed by the clamp tonnage, to provide a chamber or bag surrounding the honeycomb. Prior to “bagging”, an epoxy adhesive was applied to the interior surface of the Nylon film. The epoxy adhesive was a 250° F. supported film adhesive such as Redux 382H or Redu...

example 2

Mismatch Thermoplastic / Thermosetting Materials, Some Adhesive Necessary—FIGS. 1 and 4

[0041] A sandwich panel in accordance with the present invention was prepared using HEXWEB prime cure aramid honeycomb as the core material. The honeycomb was not perforated for internal ventilation, as it is somewhat porous and had a cell size of {fraction (3 / 16)} inch. The core was 11.5 inches long, 11.5 inches wide and 1.00″ inch thick. The honeycomb was placed between two sheets of CAPRAN 980 Nylon 6 Film 0.003 inches thick, available from Honeywell Corp, that acts as an adhesive. CAPRAN 526 Nylon 6 / 6 film that was 0.003 inch thick by 15 inches wide and 15 inches long overlapping the edges of the honeycomb and adhesive films forms the barrier. The resulting flashing of Nylon film surrounding the honeycomb is sealed by the clamp tonnage, to provide a chamber or bag surrounding the honeycomb.

[0042] TOWFLEX TFFEG 682 2×2 N6:30% Nylon 6 / E Glass prepreg skins (available from Hexcel Corp.) were appli...

example 3

All Mismatched Thermoplastics where Adhesives are Necessary and Surfacing Film—FIG. 6

[0044] A sandwich panel in accordance with the present invention was prepared using HEXWEB EM polyester / nylon honeycomb as the core material. The honeycomb is porous and had a cell size of {fraction (3 / 8)} inch. The core was 11.5 inches long, 11.5 inches wide and 1.00″ inch thick. The honeycomb was placed between two sheets of 0.002 inches thick Polyolefin Film that acts as an adhesive (available from Bemis, Shirley, Mass.). CAPRAN 526 Nylon 6 / 6 film that was 0.003 inch thick by 15 inches wide and 15 inches long overlapping the edges of the honeycomb and adhesive films forms the barrier. The resulting flashing of Nylon film surrounding the honeycomb is sealed by the clamp tonnage, to provide a chamber or bag surrounding the honeycomb. Again two layers of Polyolefin film acting as adhesive are placed on either side of the assembly. These adhesive layers may be necessary when the various polymeric com...

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Abstract

Composite sandwich panels that include a core having a permeable body that is sandwiched between two skins. An internal barrier is located between the skins and the core to provide an impermeable chamber surrounding the permeable core. The chamber is pressurized during formation of the panel to provide an interior counter pressure against the mold / press used to form the panel. The counter pressure applied by the chamber reduces the amount of voids in the skins and improves the surface finish of the skins. In addition, the impermeable material remains within the finished panel to provide an internal barrier surrounding the core.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to structures that include a core sandwiched between two skins to provide a lightweight and structurally strong panel. Such structures are commonly referred to as “sandwich panels”. More particularly, the present invention is directed to improving the quality of the skins and the overall sandwich panel by internally pressurizing the panel during the molding process. [0003] 2. Description of Related Art [0004] Sandwich panels have been used widely in all types of situations where light weight and high structural strength are required. Sandwich panels have been used extensively in the aerospace industry. For example, sandwich panels are used in aircraft structural parts and control surfaces as well as floorboards and other interior panels. Sandwich panels are also popular in the automotive industry where their ability to absorb relatively large amounts of impact energy is an imp...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B32B3/12E04C2/36
CPCB32B3/12B32B37/0007B32B2305/022Y10T428/236Y10T428/24165Y10T428/239E04C2/365B32B7/12B32B15/08B32B2323/10B32B2367/00B32B2377/00
Inventor SMITH, LANCE D.WALSH, PAUL
Owner HEXCEL
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